How many partitions are too many? Who gets to decide? Is the answer written down somewhere, and has anybody opened that page since the last reorg? ACLs can't help here, because they answer whether a principal may issue a command at all, and they never read the command. A sensible topic request and a hundred-partition one look identical to them, so platform teams cover the gap with wiki conventions, manual review, or custom tooling, and all three get harder as more teams share the cluster.
The [_Request Rule Validator policy_](https://developer.konghq.com/event-gateway/policies/request-rule-validator/)_Request Rule Validator policy_ is Event Gateway's traffic control policy for this. You write rules against the contents of a Kafka request, like partition count, replication factor, topic and consumer group naming, and ACL bindings. It also reaches into client settings, so you can require producers to acknowledge writes from all in-sync replicas. Each rule is an expression describing what a valid request looks like; when the expression evaluates to false, the rule's action *runs*.
There are two actions:
- - **Reject:** the gateway responds with Kafka's POLICY_VIOLATION error code and doesn't forward the request to the backend cluster, so the client gets a standard Kafka error instead of a hung connection.
- - **Passthrough:** the request goes through, and the gateway records the violation in metrics and logs.
Batched requests get equal treatment. When a create-topics request carries several topics, and one breaks a reject rule, only that topic is rejected, and the rest go through. One more tip from the docs: put the validator after your ACLs policy, so a client that isn't authorized learns nothing about your rules before it gets turned away. Once you configure a create-topics rule, the gateway turns off automatic topic creation on metadata requests, so clients can't skip your rules by auto-creating topics.